Ab initio molecular dynamics using density-based energy functionals: application to ground-state geometries of some small clusters

Abstract

The ground-state geometries of some small clusters have been obtained via ab initio molecular dynamical simulations by employing density-based energy functionals. The approximate kinetic-energy functionals that have been employed are the standard Thomas-Fermi (T_TF) along with the Weizsacker correction T_W and a combination F(N_e)T_TF+T_W. It is shown that the functional involving F(N_e) gives superior charge densities and bond lengths over the standard functional. Apart from dimers and trimers of Na, Mg, Al, Li, and Si, equilibrium geometries for Li_nAl, n=1,8 and Al₁₃ clusters have also been reported. For all the clusters investigated, the method yields the ground-state geometries with the correct symmetries with bond lengths within 5% when compared with the corresponding results obtained via the full orbital-based Kohn-Sham method. The method is fast and a promising one to study the ground-state geometries of large clusters.